Possibility of Subelectron Noise With Room-Temperature Silicon Carbide Pixel Detectors

Pixel radiation detectors made on epitaxial silicon carbide are presented. Two small-format prototypes have been fabricated: a 4times4 matrix with pixels of 400times400 mum² and 6times6 matrix with 200times200 mum² pixels. Typical leakage currents between 3 fA and 10 fA for the larger pixel size, and between 0.1 fA and 4 fA for the small pixels have been measured at 27 degC, corresponding to current densities between 0.25 and 10 pA/cm². In terms of equivalent noise charge, the contribution of most of the pixels is lower than 1 electron root mean square (rms) up to peaking times of tens of mus of pulse shaping. These pixel detectors are ready for applications in ultimate-resolution X-ray spectroscopic imaging at room temperature when a suitable ultra low noise front-end electronics, presently not available, will be developed. An analysis of the experimental data on these detectors coupled to front-end transistors of commercial CMOS technologies is presented, indicating that a noise level of around 4-electrons rms can be achieved at room temperature, limited by the front-end 1/f noise. The conditions to fully exploit the SiC pixel capabilities are quantitatively analysed by considering CMOS technologies for front-end and preamplifier design and the continuous progress in the SiC growing processes